Like many inventors who were sure they had come up with a "better mouse trap", this inventor spent some ten years repairing and rebuilding rock pulverizing machines, that took rock that had been previously crushed in a jaw crusher to 3/4" and then pulverizing it to a fine powder in a Raymond Roller mill or similar mill. In the extremely dusty environment inside the grinding mill the contaminating dust combines with the lubricating oil or grease to form a very potent grinding compound. In a short time this grinding compound wears out the bronze bushings and steel shaft, which then requires their repair or replacement.
Maintenance on these mills is quite costly and time-consuming. The parts that need most frequent repair are the journals, the parts that actually take the load of grinding the rock to a fine powder. The journals eventually begin to wobble or may even freeze up. The cause is simple. Contaminants enter the journal and wear out the bearings. In the industry, the life of a journal before it needs repair or replacement might be estimated at only two months. Contaminants from the various kinds of rock take differing lengths of time before the bearings become a problem. Journals for pulverizing rock for talc require much earlier repair than those used for pulverizing limestone. With current journal design it is only a matter of differing lengths of time before the journals must be repaired or replaced.
Taking out and replacing worn-out bearings on the journals is time-consuming. When a mill must be temporarily shut down while the journals are repaired, downtime is costly. Damaged journals have to be removed from the grinding mill. The task of repairing the journals is itself difficult. It may take several hours with a sledge hammer just to break the journal apart. Then the bronze journal bearings, which have suffered a great deal of wear, must be removed and either replaced by new ones or rebuilt. Usually defective bearings are simply replaced. The shaft, however, may need to be built up by welding to return the outside diameter to fit the new or renewed bronze bushings.
There is one major reason for the breakdown of these journals. Contamination from the rock grindings can not be prevented from entering the bearings, and once in the bearings there is no way contaminants can be removed or purged from the journal apart from taking the entire journal apart. It is only a matter of time before enough contamination entering the bearings leads to their breakdown and the necessity of replacing or repairing them.
Then there is the further problem that gradually the roll begins to fidget and wobble o the roll mount and eventually damages the main shaft. In the prior art there was no way to maintain tension to prevent this from happening.
Consideration of the prior art as shown in FIG. 6 demonstrates the problem. This figure shows the journal currently in use in the Raymond Roller Mill, which, with slight modification, has been in use for about half a century. Lubricant is intended to exit the journal at the slinger ring; there is nothing, however to prevent contaminants from entering the bearings at the same point.
There is an obvious need for improvement in the general design of these journals. Such a design needs to incorporate a method by which contaminants can be kept away from the bearings. Additionally a new design needs to prevent the damage to the shaft caused by wobbling and fidgeting.
This invention provides the method of keeping the dust and lubricant apart by preventing the lubricant grease from commingling with the dust, by forcing the lubricant to pass through a labyrinth seal comprised of the main shaft and three round concentric tubes whereby the lubricant passes through the labyrinth from top to bottom as shown in FIGS. 1,2,3, and 5, and at the same time preventing the contaminating dust from going backward in the reverse direction from the normal flow through the labyrinth. In the process of adapting this system to existing journals, applicant has also discovered other alterations in the design which further improve overall performance.
The first prototypes, which were tested in 1984, had problems which needed to be addressed.
The problem of keeping the rollmount on the shaft was first solved by providing a locking key. Later this was discovered to be unnecessary. A tapered friction locking system was found to be totally adequate. The shaft is given a 2.degree. taper where it meets the roll mount and the roll mount is given a 6.degree. taper. Once mounted, it can not easily be forced apart.
At first applicant attempted to retain the half century old bronze bearing design. It was found that although this might be done, they could not provide the long life that modern bearings can provide. They have been replaced with modern Timken type tapered roller bearings.
A further improvement which has not yet been added to the prototype, is to add a microdot temperature sensor which would serve to warn the equipment operator to check the lubricant in the system or to warn of possible trouble.
The preferred embodiment, as described in this application, has been tested now for over a year and found to be reasonably free of problems. Thus applicant has reached the conclusion that with the preferred embodiment of his invention, for all practical purposes the problem of contamination and subsequent early breakdown of roller mill journals has been solved.
Applicant's major improvement to the journal design has been to add the unique labyrinth seal tube system which prevents contaminants from reaching the bearings.